Plating process



Patented Aug. 24, 1943 Du-Repcl Corporation, Indianapolis, Ind., a corporation of Indiana I No Drawing. Application January 9, 1940,

Serial No. 813,140

3 Claims. (01. 204-34) The present invention is an improvement in processes for plating chromium upon a metallic base and is more particularly directed to a process for chromium plating members of a Linotype machine subjected to contact with molten type metal.

Certain members of a Linotype machine such as, for example, spacebands, molds, liners, cams and matrices of line casting machines, receive upon their surfaces dross from the type metal used during the operation of the Linotype ma chine and it is desirable to maintain the surface of these members clear from this dross by applying a coating to the member to which type metal, that is, an alloy of lead with antimony or lead and other lead alloys will not adhere. Further, certain of these members, such as the spacebands and the liners, should have a hard, smooth surface which does not vary when subjected to temperatures of from room temperature to above 400 F., whereby the need of lubrication, such as graphite or oil, together with frequent brushing and cleaning of the members can be eliminated.

The principal object of the present invention is to provide a process for producing members having a surface to which type metal or its dross will not adhere, which requires no lubricating, cleaning or like attention and which adheres tightly to its base regardless of any ordinary temperature changes to which it may be subjected.

Other objects of the invention will in part be obvious and in part pointed out in the following detailed description of the process forming the present invention.

Th members of a Linotype machine which are subjected to contact with type metal or the dross thereof are formed with steel comprising the principal element thereof. Using a spaceband which is used for justifying lines of matrices as-.,

sembled from the keyboard of matrix composing and line casting machines as an example of one member of a Linotype machine which is to becoated according to the present invention, the steel spaceband is placed in a boiling cleaning solution such as is normally used in plating rooms and which has as the principal ingredients thereof soda ash, tri-sodium phosphate, resin soap and lye. The steel spaceband, while suspended in this boiling solution, is made cathodic and then anodic by alternately connecting the spaceband to the opposite poles of a current supplying means and passing electrical current therethrough.

sition of this bath is approximately 66% sulphuric acid, 5% glycerine and the balance water or may be a straight sulphuric acid bath to which has been added a trace of copper sulphate, with no other water than that contained in the sulphuric acid. The spaceband, while in this bath, is made the anode for a short period. The spaceband thus treated, that is, being made anodic in either of the two solutions, prepares the surface thereof so that it is particularly receptive to metallic attachments. An apparent condition of passivity is reached which aids in the subsequent attachment of a metallic coating by electrolysis, whereupon, said coating becomes more firmly connected thereto than is possible in previously known electroplating.

The spaceband is then rinsed in cold water, placed in a chromic acid plating bath whereupon a hard chromium coat having a, total thickness of approximately .00025 inch or more will be fanned thereon by using between to 2 amperes of current per square inch. The coated spaceband is then rinsed and allowed to cool down slowly. It is important that the coated spaceband be slowly cooled, as this greatly affects the permanence of the attachment of the chromium to the steel base.

To correctly efiect this slow cooling of the coated spaceband, the band can be placed in molten lead which is at a temperature slightly above its melting point and the combination thereof placed in a suitable metallic container where they are allowed to slowly cool.

The spaceband so treated by the foregoing procedure has the chromium coat thereon integral with the steel base and this causes the chromium coat to firmly adhere to the steel at all times and under all working conditions.

A modification of the principal procedure of forming the coating comprises in depositing a thin film of from about .0001 inch to about .0002 inch of a metal, whose coefficient of expansion is less than iron and which will not oxidize readily at about 400 F., on the steel spaceband by electrolysis immediately after the spaceband has been made anodic by steps similar to the first portion of said principal procedure. The metal preferably used by me for this first coating is either nickel, copper, or cobalt. The spaceband thus coated has the nickel, copper, or cobalt firmly attached to the base metal and the same can be stored for a considerable period of time before finishing with an outside chromium plate. The nickel, copper, or cobalt plated spaceband is made anodic and chromium plated by the same steps as are used in chromium plating the base steel according to the principal procedure.

The intermediate coating of cobalt, copper, or

, nickel compensates for the diflerence of the costeel base and the present invention contemplates treating other members than spacebands. The processes are capable of considerable modiflcation and such modifications thereof as come within the scope of my appended claims, I deem to be a part of my invention.

I claim:

'1. Process for plating chromium upon a metallic member comprising placing said member in a boiling cleaning solution, making said member alternately cathodic and anodic while in said solution, rinsing said member after removalfrom said solution, making said member anodic while in a sulphuric acid-glycerine bath consisting of 66% sulphuric acid, 5% glycerine and the balance. being water, plating said member with chromium by electrolysis in a chromic acid plating bath where the temperature oi. said member is elevated, and then placing said member in a mass of slowly cooling molten material.

2. Process for chromium plating a steel member comprising placing said member in a boiling cleaning solution, making said member alternately cathodic and anodic while in said solution, rinsing said member after removal from said solution, making said member anodic for a short period of time while in a sulphuric acidglycerine bath consisting of 66% sulphuric acid, 5% glycerine and the balance water, electrically plating said member with a metal whose coeilicient of expansion is less than that of iron and which will not oxidize readily at about 400-F.,

making said plated member anodic for a short period of time while in the sulphuric acidglycerine bath, electrolytically plating said plated member with chromium whereat the temperature thereof will be elevated, placing said heated chromium plated member within a molten lead which is at a temperature slightly above ,its melting point and cooling said molten lead ness of between .0001 inch and .0002 inch, making said plated member anodic for a short period of time while in the sulphuric acid-glycerine bath, electrolytically plating said plated member with chromium whereat the temperature thereof will be elevated, placing said heated chromium plated member within a molten lead which is at a temperature slightly above its melting point and cooling said molten lead and chromium plated member slowly.

JAMES w. SPENCE. 

